[Patent Document 1] JP-A-2003-130628
In recent years, vibration problems have occurred in structures such as offices, enterprise buildings, multiple dwelling houses, and conventional homes due to vibrations attributable to metal working machines, compressors, and the like which are used in factories, business establishments, and construction sites, or due to such as the vibration of the ground and road surfaces attributable to earthquakes or vehicle travel. As a vibration control measure for such a conventional home or the like, it is conceivable to use active dynamic vibration absorber using active control. In ideal active control, however, it is necessary to detect such as the absolute displacement and the absolute velocity of the structure as a controlled object, i.e., a vibrating body (detection object), in a case where it is subjected to vibration. In that detection, a seismic-type displacement sensor (hereinafter referred to as the displacement sensor) which is directly attached to the controlled object is suitable.